Preparation, Properties And Mechanism Of Soy Milk Tea

Soy milk powder contains high quality plant protein and isoflavones, and its amino acid composition is closed to milk protein. It is also cholesterol free, budget friendly, and preferred by consumers. Many women regard soy milk powder as daily drinks. Superfine green tea powder is a modern superfine grinding technology to produce pure natural ultrafine green tea powder and keeps the nutritional in the large extent. Superfine tea powder is widely used in all kinds of food. Taking soy milk powder and superfine green tea powder as the main raw materials to get the soy milk tea will not only keep the nutritional value of soy milk, but also have tea flavor and health benefits. The development of soy milk tea is a new way of utilizing soy milk powder, which may provide a basis of enhancing additional value of soy milk powder in theory and practice.First of all, fuzzy organoleptic evaluation was used to investigate formula test of the ratio of soy milk powder and green tea powder, sweeteners and vanillin. The all acceptability was inferred from scores of color, taste and smell, appearance and mouthfeel. The results of orthogonal test showed the optimal formula: the proportion of soy milk powder and tea powder was 15:1, sweetener was 13%, vanillin was 2.0%.Secondly, the influence of stabilizers on soy milk tea after rehydration was studied. Using layered ratio and suspension stability as indices, the results showed that xanthan gum, arabic gum and guar gum were suitable stabilizers. The results of orthogonal test showed the optimal formula was 0.6%xanthan, 0.6%gum guar and 0.2% arabic gum. Then the influence of rehydration condition on the quality of soy milk tea was explored. Results showed the best water temperature was 75 ℃ and the best water volume was 8 times of the weight of soy milk tea.Again, the protein digestibilities of soy milk tea in gastrointestinal digestion were investigated. The results showed that the protein digestibilities of soy milk tea containing different tea powders in simulated gastric and intestinal fluid were different. In simulated stomach digestion, intestinal digestion and total simulated gastrointestinal digestion, with the increasing of tea powders, the protein digestibilities of soy milk tea reduced.Finally, the impact mechanisms of gastrointestinal digestion of tea polyphenol towards soy protein were investigated. The results showed that with the presence of tea polyphenol, soy protein was harder to be digested in the pepsin solution at p H 2 and pancreatin solution at p H 7.5. Fluorescence and UV spectra showed that tea polyphenol formed complex with soy protein and made the structure of soy protein change at p H 2 and p H 7.5. FTIR showed, under the condition of p H 2, when the ratio of soy protein and tea polyphenol was 1:0.2, tea polyphenol increased α-helix of soy protein and reduced its random coil; when the ratio of soy protein and tea polyphenol was 1:1, tea polyphenol reduced α-helix of soy protein, made radom coil reduced more compared to 1:0.2. Under the condition of p H 7.5, when the ratio of soy protein and tea polyphenol was 1:1, tea polyphenol increased α-helix of soy protein and reduced its random coil; when the ratio of soy protein and tea polyphenol was 1:0.2, tea polyphenol reduced α-helix of soy protein, made radom coil reduced more compared to 1:1. The results showed that, under the condition of p H 2 and p H 7.5, tea polyphenol might change the structure of soy protein and make it more closely, and harder to be digested. So tea polyphenol-substrate(tea polyphenol-soy protein) was another mechanism of tea polyphenol affecting digestion of soy protein. Different changes of second structure of soy proteins affected by tea polyphenol might also result in the difference of digestibility.